're learning more about the troubled background of adam lanza. a new investigation by pbs finds that lanza was diagnosed with a sensory disorder, was very shy and liked being touched only by his mother. as for the exposure to guns, friends say lanza's mother nancy loved shooting because it helped her bond with her son. >> extraordinary reporting. this is kind of one of the summary graphs of the story, what emerges in this exploration of a still unfolding story is a portrait of a mother apparently devoted but perhaps misguided, struggling to find a place for her son in society. and a boy exceptionally smart in some areas, profoundly deficient in others, who never found a place in the world. >> it's just so sad because of the outcome of this. you think when you look at what happened in their life, you think if she had just made a different decision somewhere along the way, this could have been avoided. and everybody points to the guns, and that being the wrong decision that she made. but perhaps it's not the guns. maybe it's the type of help she got for her son and it wasn't adequate enough.